Web offset inks

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Inks. Basic raw materials for letterpress inks, such as mineral oils, soya bean oil, resins, and pigments, are essentiaHy the same as those used in web offset inks. Inks are tinctoriaHy weak, relatively fluid, and their low and high shear viscosities are low. 

In Japan, the standard Eco Mark Product Category No. 102 Printing Ink Version 2.6 [26] sets on a voluntary basis standards for an environmentally friendly composition of printing inks. Since introduction of this standard in 1997, more than 90% of all offset inks in Japan were reformulated to inks free from aromatic compounds ( white oil ). To fulfil the above-mentioned standard, the inks should be based on vegetable oils. They should not contain more than 1 vol.% of aromatic hydrocarbons ( white oils ). Additionally, sheet-fed offset inks should not contain more than 30% of crude oil-based solvents and not more than 3% VOC. Web offset inks should contain no more than 45% crude oil solvents (which seems not really to be a progress in comparison to typical standard inks). By the way, it is expected from vegetable oil-based inks that the print products are as deinkable as conventional mineral oil-based offset inks. 

Temperatures of up to 100°C and higher may be observed as P.R.57 1 is dispersed in offset printing inks, especially in web offset inks by means of modern dispersion equipment. This is especially true for agitating pearl mills. Printing inks and prints may undergo color shifts if they are exposed to these conditions. The process, which is reversible, is caused by release of the water of crystallization from the pigment. 

QuickspcrsetSt [BASF AG] Cone, pigment pastes in qiedal varnishes for web offset inks. 

Web Heat-Set Publication and Commercial Inks. Almost all heat-set inks are now printed on web offset presses, and are based on vehicles containing synthetic resins and/or some natural resins. These are dissolved in hydrocarbon solvent fractions which are specially fractionated for use in the ink industry. They vary in boiling range between 180 and 300 °C. Small percentages of alkyd resins (qv) may be contained in these inks. They dry in less than one second by means of solvent evaporation in a heatset oven. These ovens utilize high velocity hot air to raise the web temperature to 120-150 °C. 

Their main disadvantage is that the heat of vaporization of water is greater than that of the organic solvents usually used, e.g., 1043 BTU/ lb as compared with about 180 BTU/lb for toluene, methyl ethyl ketone, and ethyl acetate. Also, the utility of these inks is limited they cannot be used in letterpress printing because they dry too rapidly on open roller systems, and they cannot be used in web-offset lithography because they are miscible with the aqueous fountain solution. Moreover, the water may swell the paper substrate and give poor register, and paper printed with some water-based inks cannot be recycled in the presently-used processes. 

Syntbe-Cal . [Arizona] Thermofdas-tic hydrocarbon resin us fw web offset news inks and vehicles. 

Chem. Descrip. Micronized synthetic wax CAS 8002-74-2 EINECS/ELINCS 232-315-6 Uses Rub resist, aid, abrasion resist, aid, slip agent in printing inks, esp. water- and alcohol-based flexo and gravure inks and web offset heat-set inks... 

Chem. Descrip. Polyethylene wax CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses Mar resistance aid, slip agent for printing inks (IR, UV, heat set web offset, sheetfed), metal decorating paints/coatings, high gloss overprint varnishes... 

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